BEIRUT, Feb 23 (Reuters) - A new wave of bombs struck Syria's eastern Ghouta unabated on Friday, witnesses said, ahead of a U.N. Security Council vote to demand a 30-day ceasefire across the country.

For a sixth straight day, warplanes have pounded the densely populated agricultural pocket east of the capital, the last rebel bastion near Damascus.

The recent escalation has killed at least 426 people and injured hundreds more, the Syrian Observatory for Human Rights monitoring group says. The dead include at least 98 children.

Medical charities say jets have hit more than a dozen hospitals, making it near impossible to treat the wounded.

The Britain-based Observatory said government warplanes and artillery hit Douma, Zamalka, and other towns across the enclave in the early hours on Friday.

There was no immediate comment from the Syrian military.

A witness in Douma who asked not to be identified said by telephone that the early morning bombing was the most intense so far. Another resident, in the town of Hamouriyeh, said the assault had continued "like the other days".

"Whenever the bombing stops for some moments, the civil defence vehicles go out to the targeted places. They work to remove the debris form the road," said Bilal Abu Salah.

The bombing of eastern Ghouta since Sunday night has been among the fiercest of the war, now entering its eighth year.

The Civil Defence in eastern Ghouta said its rescuers rushed to help the wounded after strikes on Hamouriyeh on Friday morning. The emergency service, which operates in rebel territory, says it has pulled hundreds of people from under the rubble in recent days.

CEASEFIRE ATTEMPTS

Damascus and Moscow say they only target militants, and that they aim to prevent rebels from firing mortars at the capital. They have accused insurgents of holding residents as human shields in the Ghouta.

Syrian state news agency SANA said on Friday that factions in the besieged suburbs shelled neighbourhoods of Damascus. The army was pounding militant targets in response, it said.

Hamza Birqdar, the military spokesman for the Jaish al-Islam rebel faction, said it had thwarted nine attacks by pro-government militias trying to storm a front in the southeast of the Ghouta.

Nearly 400,000 people live in eastern Ghouta, a pocket of satellite towns and farms that has been under government siege since 2013.

The U.N. envoy for Syria has pleaded for a truce to halt one of the worst air assaults of the seven-year war and prevent a "massacre". Staffan de Mistura renewed his call on Friday to stop both the "horrific" bombing of besieged eastern Ghouta and indiscriminate mortar shelling on Damascus.

The U.N. Security Council was considering a resolution, which Kuwait and Sweden drafted, demanding "a cessation of hostilities throughout Syria for all military operations" for 30 days to allow aid deliveries and medical evacuations.

The vote is set to take place on Friday. The resolution does not cover the groups Islamic State, al Qaeda and the Nusra Front, which Moscow and Damascus say they have targeted in eastern Ghouta.

Several previous ceasefire attempts in Syria have quickly unravelled throughout the multi-sided conflict, which has killed hundreds of thousands and displaced 11 million people.

(Reporting by Ellen Francis; Additional reporting by Michelle Nichols in New York; Editing by Tom Perry and Peter Graff)